Digital processing devices can be attacked by other digital processing devices with which they are communicating. Accordingly, some digital processing devices only accept communication from devices that they trust. A device can establish trust of a requesting device by, for example, examining information identifying the requesting device or information describing the type or configuration of the requesting device. However, such information may not always be a useful predictor of whether a device is, for example, already infected by malicious software, likely to launch attacks, and/or likely to become infected by malicious software.
Furthermore, in some types of networks, for example, in mobile ad-hoc networks (MANETS) which can have, for example, no central control, no wireless switches, no base stations, and can have devices entering and leaving the network dynamically, decisions of whether to trust communications can be especially challenging due to the quickly changing topology and membership of the network. For example, an intrusion detection system can perceive packet dropping or communication from unknown outside digital processing devices as an indication of attack. However, such occurrences can be commonplace and benign in MANETS.